Recently to solve a problem I have been encountering related to iCloud, I had to sign out of iCloud and sign back in.
Normally I have all the options enabled except for mail. When I signed in I started enabling all of the features and came across a problem where if I were to attempt to enable Calendar while Reminders is enabled, Calendar would say the words "Setting Up" and a spinner would appear and the checkbox would be greyed in. After about 20 seconds the words, spinner and checkbox clear away leaving Calendar still disabled.
This works the other way around if Calendar is enabled first and I attempt to enable Reminders.
I have tried extremely basic things such as rebooting the system to clearing the cache files in the libraries but still nothing. Anyone got any ideas on how to fix this? Thanks!